20720291 has 4 divisors (see below), whose sum is σ = 20871672. Its totient is φ = 20568912.

The previous prime is 20720261. The next prime is 20720299. The reversal of 20720291 is 19202702.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20720291 - 2¹⁰ = 20719267 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20720299) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 75485 + ... + 75758.

It is an arithmetic number, because the mean of its divisors is an integer number (5217918).

Almost surely, 2^20720291 is an apocalyptic number.

20720291 is a deficient number, since it is larger than the sum of its proper divisors (151381).

20720291 is a wasteful number, since it uses less digits than its factorization.

20720291 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151380.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 20720291 is about 4551.9546350991. The cubic root of 20720291 is about 274.6620244670.

Adding to 20720291 its reverse (19202702), we get a palindrome (39922993).

The spelling of 20720291 in words is "twenty million, seven hundred twenty thousand, two hundred ninety-one".